Plastic shipping and storage containers are widely used in national and international commerce. Containers protect and support their contents during storage and shipment and there is an increasing demand that containers be effective in helping to maintain the quality of their contents.
A particularly useful shipping and storage container is the pallet (a structural platform made of metal, wood, or plastic materials). Wooden pallets have been in use for a number of years but they tend to be heavy, bulky, and expensive to make and maintain. Additionally, they are subject to deterioration due to adverse weather and can fail due to rotting when wet. Additionally, wooden pallets are fastened together by means such as glue, nails, staples, etc. Inclement weather also accelerates deterioration of these fastening means.
The potential for infestations by insects has created increasing demand for treatment of wooden pallets prior to export. Since Oct. 1, 2001, for example, the European Union requires heat or chemical treatment for all coniferous non-manufactured wood packaging. Shipments that do not comply may be refused at the border; more likely, non-compliant packaging will be destroyed at the shipper's expense.
Metallic pallets also present problems. Typically, they are expensive, heavy and subject to corrosion.
Plastic pallets overcome many of the problems of wooden and metallic pallets, but they present problems of their own. During fires they are subject to flowing, which results in molten plastic spreading heat and fire. The National Fire Protection Association has passed stringent regulations that have diminished the utility of plastic pallets.
References disclosing plastic pallets are known. WO 00/20495 discloses high performance plastic pallets having a composition comprising a thermosetting resin, which can be an epoxy resin, as well as a plurality of thermoplastic resins. The composition can include, for example, flame retardants. No polyolefin is disclosed. U.S. Pat. No. 5,879,495 relates to constructions of polyvinyl chloride pallets. WO 00/05143 discloses plastic pallets having a polyolefin top deck and a polycarbonate or polyphenilin derivative bottom deck. JP 11278485 relates to polyolefin/halogenated epoxy compositions useful to make a pallet. The halogenated epoxy acts as a flame retardant, optionally in combination with a second flame retardant.
U.S. Pat. No. 4,428,306 discloses a thermoformed pallet constructed of a thermoplastic resin material. A film to create a laminated non-skid surface is provided.
U.S. Pat. No. 4,051,787 discloses a plastic pallet having a deckboard provided with a rubber anti-slip member or coating. U.S. Pat. No. 6,006,677 provides a synthetic resin pallet with a slip-resistant scuffed texture surface, created by brushing the surface with a cup-shaped wire brush.
Plastic pallets having a foamed structure have been disclosed. U.S. Pat. No. 3,581,681 relates to structural foamed pallets comprising a variety of components including polyolefin and epoxy. No additives are included in their compositions. U.S. Pat. No. 4,375,265 discloses a one piece molded pallet container comprising a foam composition comprising a variety of thermoplastic resins, for example, polyethylene, polyphenylene oxide, polyamide, and others. No epoxy resins are disclosed, nor are any additives. Thermoplastic thermoset hybrid foams have been disclosed in WO 01/23462 having use as flexographic mounting tapes. No molded articles are disclosed.
U.S. Pat. No. 5,709,948 discloses semi-interpenetrating polymer networks (semi-IPNs) of epoxy and polyolefin resins useful, for example, as tape backings, fibers, coatings, foamed constructions, and molded foamed parts.